Personal safety is a major concern. Streets of our cities are unsafe. Manufacturers have offered different devices to assist with crime deterrence.
Mace and/or pepper spray is one such attempt at deterrence. However, it is far from an adequate solution, since it can be turned against the owner with little effort. Even if not, many attackers, especially those with drug additions or mental illnesses, may be largely or completely oblivious to this kind of pain.
Another possibility is to carry a real weapon, such as a gun. As with the mace, the gun can be turned against the owner. Moreover, even a person properly defending themselves can be sued for injuring the attacking criminal.
A personal alarm can be activated when one feels danger. The rationale is that the attacker will flee when the personal alarm is activated.